The most recently described and most common inherited defect associated with increased risk of thrombosis is a single point mutation in the factor V gene leading to an activated factor V that is resistant to inactivation by partial thromboplastin time (APTT) after addition of activated protein C screens for the defect. This will be a 2-phase study to evaluate a series of newborn infants born at University Hospital for the factor V mutation using the functional assay for APCR, the modified assay for APCR and the DNA test for the factor V mutation. Phase I will focus on determining prevalence of APCR and factor V mutation in 100 infants. Phase II will determine whether the factor V mutation in neonates increased their risk for catheter-related thrombosis.